Image forming apparatus

ABSTRACT

An image forming apparatus includes: an image forming unit configured to perform image formation in a first mode, in which image formation is performed by a plurality of image forming stations, or a second mode, in which image formation is performed by a predetermined image forming station among the plurality of image forming stations; and a controller configured to: control the image forming unit to perform a preparation operation in accordance with color mode information; set a restricted operation state in which the controller prohibits the image formation in the first mode and permits the image formation in the second mode when any one image forming station, except for the predetermined image forming station, is incapable of performing image formation; and prevent the image forming unit from performing the preparation operation when the first mode is set as the color mode information and the restricted operation state is set.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an image forming apparatus, such as acopying machine and a printer, which is configured to perform imageformation on a recording material through an electrophotographic method,and more particularly, to a print preparation operation of the imageforming apparatus.

Description of the Related Art

In a color image forming apparatus employing an electrophotographicmethod, a toner image formed on a photosensitive drum is transferredonto an intermediate transfer belt by a primary transfer roller arrangedopposed to the photosensitive drum, and this process is repeated foreach of a plurality of toner colors. With this, a full color toner imageis formed on the intermediate transfer belt. A color image formingapparatus of a so-called tandem type has become the mainstream. In theimage forming apparatus of the tandem type, four photosensitive drums,which are configured to form toner images of yellow, magenta, cyan, andblack, respectively, are arranged in a rotating direction of theintermediate transfer belt, and the toner images formed on thephotosensitive drums are sequentially transferred onto the intermediatetransfer belt. The color image forming apparatus have been demanded toshorten a first print output time (hereinafter also referred to as“FPOT”) and a first copy output time (hereinafter also referred to as“FCOT”). The FPOT is a period of time from input of a print instructionto output of a first recording material. The FCOT is a period of timefrom pressing of a copy key to output of a first recording material as acopy of an original. As a method of shortening the time, there has beenwidely used a technology of performing a print preparation operationbefore input of an instruction to start printing or an instruction tostart copying.

In U.S. Pat. No. 5,107,279, there is proposed a print preparationmethod. In the proposed print preparation method, when an operation fromwhich a print instruction is predicted, such as an operation to anoperation unit of an image forming apparatus or placement of an originalto an original reading device, is detected, rotation of a scanner motoris started prior to the print instruction. In general, the scannermotor, which is configured to drive a rotary polygon mirror of anoptical scanning device, requires longer time from the start of rotationto stabilization of the rotational speed as compared to other motorsnecessary for image formation such as a drive motor configured to drivethe photosensitive drum. Thus, rotation of the scanner motor is startedbefore the print instruction is received. Such a configuration isadvantageous in that printing can be started without a standby time fromthe input of the print instruction to the stabilization of the rotationof the scanner motor.

In the color image forming apparatus, selection can be made from twocolor modes including a full color mode of performing image formationwith a full color image and a monochromatic mode of performing imageformation with a black and white image. In the related art, a printpreparation operation control is not switched in accordance with thecolor mode setting, with the result that the print preparation operationcontrol is not optimum. In view of this, the print preparation operationcontrol can be optimized through switching of the print preparationoperation control in accordance with color mode setting which is setthrough the operation unit. However, for example, there is a problemthat, when color toner is used up, and only the monochromatic printingcan be performed, the print preparation operation performed inaccordance with the color mode setting of the full color mode maydisadvantageously cause an unnecessary print preparation operationcontrol to be performed.

SUMMARY OF THE INVENTION

The present invention which has been made under such a circumstance hasan object to perform a print preparation operation control in accordancewith a state of an image forming portion.

In order to solve the above-mentioned problem, according to oneembodiment of the present invention, there is provided an image formingapparatus, including: an image forming unit including a plurality ofimage forming stations configured to respectively perform imageformation of different colors, the image forming unit being configuredto perform image formation to a recording sheet in any one of a firstmode, in which image formation is performed through use of the pluralityof image forming stations, and a second mode, in which image formationis performed through use of a predetermined image forming station amongthe plurality of image forming stations; an operation unit configured toallow input of color mode information for setting to perform imageformation in the first mode or to perform image formation in the secondmode; and a controller configured to: i) control the image forming unitto perform a preparation operation for image formation in accordancewith the color mode information before image formation when detecting anoperation from which a start instruction of image formation ispredicted; ii) set a restricted operation state in which the controllerprohibits the image formation in the first mode and permits the imageformation in the second mode when any one image forming station, exceptfor the predetermined image forming station, among the plurality ofimage forming stations is incapable of performing image formation, andthe predetermined image forming station is capable of performing imageformation; and iii) prevent the image forming unit from performing thepreparation operation when a performing the image formation in the firstmode is set as the color mode information, and the restricted operationstate is set.

According to the present invention, the print preparation operationcontrol in accordance with the state of the image forming portion can beperformed.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an image forming apparatus according to anembodiment of the present invention.

FIG. 2 is a control block diagram of the image forming apparatusaccording to the embodiment.

FIG. 3 is a flowchart for determination of a necessity of a full colorprint restricted operation in the embodiment.

FIG. 4A is a schematic front view of an operation unit.

FIG. 4B is an illustration of a pop-up setting screen.

FIG. 4C is an illustration of a display portion of the operation unit.

FIG. 5A is a sectional view of the vicinity of an intermediate transferbelt unit in a case where a full color mode is set.

FIG. 5B is a sectional view of the vicinity of the intermediate transferbelt unit in a case where a monochromatic mode is set.

FIG. 6A illustrates an abutment and separation mechanism for theintermediate transfer belt unit in an abutment mode.

FIG. 6B illustrates the abutment and separation mechanism for theintermediate transfer belt unit in a separation mode.

FIG. 7A illustrates an operation of a cam mechanism in the embodiment.

FIG. 7B illustrates the operation of the cam mechanism in theembodiment.

FIG. 7C illustrates the operation of the cam mechanism in theembodiment.

FIG. 7D illustrates the operation of the cam mechanism in theembodiment.

FIG. 7E illustrates the operation of the cam mechanism in theembodiment.

FIG. 8A illustrates the cam mechanism, an abutment sensor, and aseparation sensor in the abutment mode.

FIG. 8B illustrates the cam mechanism, the abutment sensor, and theseparation sensor in the separation mode.

FIG. 9 is a sectional view of a fixing device in the embodiment.

FIG. 10A is a graph for showing changes in temperature of a heater and atiming chart for illustrating states of supply of power to the heater.

FIG. 10B is a table for showing print preparation temperatures and aprint temperature.

FIG. 10C is a table for showing a relationship between a temperaturedifference between the print preparation temperature and a detectedtemperature, and time required to reach the print preparationtemperature.

FIG. 10D is a sectional view of the vicinity of a secondary transferportion.

FIG. 11 is a flowchart of a print preparation operation in a comparativeembodiment.

FIG. 12 is a flowchart of a control operation for the abutment andseparation mechanism.

FIG. 13 is a flowchart of the print preparation operation in theembodiment.

DESCRIPTION OF THE EMBODIMENTS

Now, an embodiment of the present invention is described in detail withreference to the drawings.

<Schematic Configuration of Image Forming System>

FIG. 1 is a sectional view of an image forming apparatus according tothis embodiment. FIG. 2 is a control block diagram of the image formingapparatus according to this embodiment. With reference to FIG. 1 andFIG. 2, a basic configuration of the image forming apparatus isdescribed.

[Schematic Configuration of Image Forming Apparatus]

A control portion 300 illustrated in FIG. 2 is configured to performsystem control on the image forming apparatus illustrated in FIG. 1. Thecontrol portion 300 includes a CPU 301, a ROM 302, a RAM 303, and atimer 291. The CPU 301 being a control unit (controller) is configuredto perform system control on the image forming apparatus. The ROM 302and the RAM 303 are connected to the CPU 301 through an address bus anda data bus. Control programs are written in the ROM 302. The RAM 303 isconfigured to store variables to be used for the control and image dataread by an image sensor 233 illustrated in FIG. 1. The RAM 303 being astorage unit is a non-volatile memory capable of retaining stored valueseven when supply of power to the image forming apparatus is stopped. Thetimer 291 capable of measuring time is connected to the CPU 301. Thus,the CPU 301 also sets a time count value of the timer 291 and acquires ameasurement value of the timer 291. The CPU 301 drives an originalconveying roller 112 and detects presence or absence of an originalplaced on an original table 152 based on a detecting result obtained byan original presence sensor 151 being a detector. Further, the CPU 301is configured to detect, through use of an image reader control portion280, opening and closing operations of an original pressure plate, andis configured to read, through use of an image sensor 233, an image ofan original placed on an original pressure plate glass plate 55 or animage of an original fed by an original feeder control portion 480. Theimage sensor 233 being a reading unit outputs information of an image ofa read original as an analog image signal to the CPU 301. The CPU 301transfers the analog image signal input from the image sensor 233 to animage signal control portion 281.

During a copy operation, the image signal control portion 281 performsvarious processes after the analog image signal input from the imagesensor 233 is converted into a digital image signal. After convertingthe digital image signal that has been subjected to the variousprocesses into a video signal, the image signal control portion 281outputs the video signal to a printer control portion 285. In the copyoperation, an operation of reading the original with the image sensor233 and performing a print operation based on the read data isperformed. Further, during the print operation performed in response toan instruction from outside, the image signal control portion 281 firstperforms the various processes on the digital image signal that has beeninput from an external computer 283 through an external interface (I/F)282. Then, the image signal control portion 281 converts the digitalimage signal that has been subjected to the various processes into thevideo signal, and outputs the video signal to the printer controlportion 285.

In accordance with an instruction from the CPU 301, the printer controlportion 285 controls image formation by the image forming portion 271,and controls feed and conveyance of a sheet being a recording materialby a sheet conveying portion 270. The image forming portion 271 includesan image forming unit 120, an intermediate transfer belt unit 140, alaser scanner unit 103, and a fixing device 170, which are illustratedin FIG. 1. The sheet conveying portion 270 includes a sheet feedingcassette 111, a multi tray 117, and a conveyance motor 272 configured todrive each conveyance roller.

An operation unit 330 is used to input color mode information for imageformation (full color mode (first instruction information),monochromatic mode (second instruction information), and automatic(third instruction information)), display a state of the image formingapparatus, and input an instruction such as an instruction to startcopying. The selected color mode information is stored in the RAM 303.

[Basic Image Forming Operation of Image Forming Apparatus]

With reference to FIG. 1 and FIG. 2, a basic image forming operation isdescribed. When the CPU 301 detects a print setting instruction, such asa color mode and digit entries input through the operation unit 330, ordetects an operation from which an instruction to start printing ispredicted, such as the opening and closing of the original pressureplate or the placement of an original, through the original feedercontrol portion 480 or the image reader control portion 280, the CPU 301performs the print preparation operation. In the print preparationoperation, the CPU 301 starts temperature control for the fixing device170 (fixing unit). Further, in accordance with the set color mode, theCPU 301 starts controlling switching of abutment and separation statesof the intermediate transfer belt unit 140 and driving of a scannermotor 274 in the laser scanner unit 103. Details of the switching of theabutment and separation states of the intermediate transfer belt unit140 and the print preparation operation are described later.

Next, when receiving the instruction to start the print operation fromthe operating portion 330, the CPU 301 starts an operation of reading animage of the original via the original feeder control portion 480. TheCPU 301 drives the original conveying roller 112 to convey the originalfrom the original table 152 onto a platen glass plate, and irradiatestoward the platen glass plate with light of a lamp (not shown).Reflected light from the original is guided to the image sensor 233through a mirror. Image data of the original that is read by the imagesensor 233 is output to the image signal control portion 281. Thereading of the original is continued until the reading of the originalon the original pressure plate glass plate 55 is completed or untilreading of an image of a final original detected by the originalpresence sensor 151 is completed.

After the switching of the abutment state of the intermediate transferbelt unit 140 is completed, the CPU 301 controls the image forming unit120 through the image forming portion 271 and starts an image formingoperation for image data stored in the RAM 303. The image forming unit120 includes, for respective colors of toner, an image forming station120 y for yellow, an image forming station 120 m for magenta, an imageforming station 120 c for cyan, and an image forming station 120 k forblack. The suffixes y, m, c, and k representing colors of toner arehereinafter omitted unless otherwise needed. Each laser scanner unit 103includes a laser light source 131 configured to emit laser light, arotary polygon mirror 133 configured to deflect the laser light emittedfrom the laser light source 131, and the scanner motor 274 being a driveportion configured to control rotation of the rotary polygon mirror 133.Further, each laser scanner unit 103 includes a mirror (not shown)configured to reflect the laser light, which is deflected by the rotarypolygon mirror 133, to the photosensitive drum 101. The laser lightsource 131 emits the laser light in accordance with a video signal. InFIG. 1, the laser light source 131 and the rotary polygon mirror 133 areillustrated only in the laser scanner unit 103 y for yellow. However,each of the laser scanner units for magenta, cyan, and black also hasthe same configuration.

The image forming unit 120 includes photosensitive drums 101respectively being a photosensitive member, developing devices 104,charging rollers 102, and photosensitive drum cleaners 107. In the imageforming unit 120, surfaces of the photosensitive drums 101 respectivelyrotated in a direction indicated by the arrow in FIG. 1 (clockwisedirection) is charged by the charging rollers 102. After that, latentimages are formed on the photosensitive drums 101 by laser lightirradiated from the laser scanner units 103 respectively being anexposure unit. The latent images formed on the photosensitive drums 101(on the photosensitive members) are developed with toner stored in thedeveloping devices 104. After that, the toner images developed on thephotosensitive drums 101 are sequentially transferred in superimpositionwith one another by primary transfer rollers 105, each having a primarytransfer voltage applied thereto, onto the intermediate transfer belt130 being rotated in the direction indicated by the arrow in FIG. 1(counterclockwise direction), thereby forming a full color toner image.The full color toner image transferred onto the intermediate transferbelt 130 is moved to the secondary transfer portion 118 by rotation ofthe intermediate transfer belt 130.

The CPU 301 drives the conveyance motor 272 through the sheet conveyingportion 270 so as to match a timing of arrival of the toner image on theintermediate transfer belt 130 to the secondary transfer portion 118.The conveyance motor 272 drives a sheet feeding pickup roller 113, sheetfeeding rollers 114, registration rollers 116, and delivery rollers 139.With this, the sheet feeding pickup roller 113 is driven to rotate sothat sheets are fed and conveyed from the sheet feeding cassette 111 oneafter another. Then, through application of a secondary transfer voltageat the secondary transfer portion 118, the toner image on theintermediate transfer belt 130 is transferred onto the conveyed sheet.The image forming apparatus of FIG. 1 includes, in addition to the sheetfeeding cassette 111, the multi tray 117 capable of placing varioustypes of sheets as a manual feeding unit enabling manual feeding ofsheets.

The sheet onto which the toner image has been transferred in thesecondary transfer portion 118 is conveyed to the fixing device 170. Inthe fixing device 170, the unfixed toner image on the sheet is heatedand pressurized so as to be fixed onto the sheet. Thereafter, the CPU301 delivers the sheet to a delivery tray 132 by the delivery rollers139 that are controlled by the sheet conveying portion 270. Theabove-mentioned image forming operation is an example, and the presentinvention is not limited to the above-mentioned configuration. In thisembodiment, the laser scanner unit 103 is provided for eachphotosensitive drum 101. That is, one laser scanner unit 103 is providedfor one photosensitive drum 101. For example, one laser scanner unit 103may perform light exposure for two photosensitive drums 101 or fourphotosensitive drums 101.

[Full Color Print Restricted Operation]

With reference to FIG. 1, a full color print restricted operation isdescribed. In the image forming apparatus, there is a case where acomponent for use in the print operation in the full color mode beingthe first mode has a failure, or a case where a cumulative amount of useof any one of the photosensitive drums has reached a predeterminedamount (hereinafter referred to as “having reached the lifetime limit”).In such cases, the CPU 301 prohibits the print operation in the fullcolor mode. For example, the photosensitive drums 101 illustrated inFIG. 1 are driven by drum motors 273 which are arranged for respectivephotosensitive drums 101. The drum motors 273 include a drum motorconfigured to drive the photosensitive drum 101 k and drum motorsconfigured to drive respective photosensitive drums 101 y, 101 m, and101 c. When any one of the drum motors configured to drive thephotosensitive drums 101 y, 101 m, and 101 c except for the drum motorconfigured to drive the photosensitive drum 101 k for black has afailure, the CPU 301 determines that the print operation cannot beperformed in the full color mode. The drum motor configured to drive thephotosensitive drum 101 k for black is hereinafter referred to as a drummotor k. The drum motors configured to drive the photosensitive drums101 y, 101 m, and 101 c are hereinafter referred to as drum motors y, m,and c, respectively. At this time, the drum motor k (not shown)configured to drive the photosensitive drum k being a component for usein the print operation in the monochromatic mode being the second modedoes not have a failure. Therefore, the CPU 301 can perform the printoperation restricted to the monochromatic printing. In this embodiment,such a functional restriction is referred to as a full color printrestricted operation (hereinafter also simply referred to as “printrestricted operation”). Through the print restricted operation, theimage forming apparatus can continue the print operation in themonochromatic mode until a service man repairs the component having afailure. Therefore, the CPU 301 can permit the image forming operationto a user. Components being triggers for the print restricted operationinclude, for example, the drum motors y, m, and c (not shown) and thelaser scanner units 103 y, 103 m, and 103 c, which are operated at thetime of printing in the full color mode, or high-voltage units (foryellow, magenta, and cyan) 275 configured to apply high voltages to theprimary transfer rollers 105 y, 105 m, and 105 c. Further, also whentoner for use in the developing devices 104 y, 104 m, or 104 c is usedup, or when the photosensitive drum 101 y, 101 m, or 101 c reaches thelifetime limit, printing cannot be performed in the full color mode.Thus, the CPU 301 performs the print restricted operation.

FIG. 3 is a flowchart for illustrating a control sequence which isstarted at the time of determining a necessity of the print restrictedoperation and executed by the CPU 301. In FIG. 3, in Step (hereinafterabbreviated as “S”) 1201, the CPU 301 determines whether or notcolor-toner empty occurs. The color-toner empty is determined based onoccurrence of a toner-empty state in the developing device 104 y of theimage forming station 120 y for yellow, the developing device 104 m ofthe image forming station 120 m for magenta, or the developing device104 c of the image forming station 120 c for cyan. When the toner-emptystate occurs in any one of the developing devices 104 y, 104 m, and 104c, the CPU 301 determines that the color-toner empty occurs, andproceeds the processing to S1207. When the color-toner empty does notoccur, the CPU 301 proceeds the processing to S1202. The developingdevices 104 y, 104 m, 104 c, and 104 k include hoppers (not shown)configured to replenish corresponding toner, and include detectingportions configured to detect the remaining amounts of toner in thehoppers. The CPU 301 determines the presence or absence of color tonerbased on the remaining amounts of toner detected by the detectingportions.

In S1202, the CPU 301 determines whether or not the color drums havereached the lifetime limit. The color drums correspond to thephotosensitive drum 101 y of the image forming station 120 y for yellow,the photosensitive drum 101 m of the image forming station 120 m formagenta, and the photosensitive drum 101 c of the image forming station120 c for cyan. When any one of the photosensitive drums 101 y, 101 m,and 101 c has reached the lifetime limit, the CPU 301 determines thatthe color drum has reached the lifetime limit, and proceeds theprocessing to S1207. When no color drum has reached the lifetime limit,the CPU 301 proceeds the processing to S1203. The CPU 301 stores, in theRAM 303, information related to the amounts of use of the photosensitivedrums 101 y, 101 m, 101 c, and 101 k from the start of use to a currenttime. A cumulative rotation time (amount of rotation) of thephotosensitive drum is used as the amount of use. Based on thisinformation, the CPU 301 determines whether or not the amount of use ofthe color drum has reached a predetermined amount to reach the lifetimelimit. The lifetime limit of the photosensitive drum may be determinedthrough another method. For example, the CPU 301 may determine thelifetime limit when a current flowing to the photosensitive drum, whichis measured by a current detection circuit of the image forming portion,is equal to or less than a predetermined value.

In S1203, the CPU 301 determines whether or not the color laser scannerunits have a failure. The color laser scanner units correspond to thelayer scanner unit 103 y configured to irradiate laser light to thephotosensitive drum 101 y of the image forming station 120 y for yellow,the laser scanner unit 103 m configured to irradiate laser light to thephotosensitive drum 101 m of the image forming station 120 m formagenta, and the laser scanner unit 103 c configured to irradiate laserlight to the photosensitive drum 101 c of the image forming station 120c for cyan. When there is a laser scanner unit 103 having a failure inthe laser scanner units 103 y, 103 m, and 103 c, the CPU 301 determinesthat the color laser scanner unit has a failure, and proceeds theprocessing to S1207. On the contrary, when no laser scanner unit 103 hasa failure, the CPU 301 determines that no color laser scanner unit has afailure, and proceeds the processing to S1204. When the motor does notrotate at the time of driving, the scanner motor 274 outputs a locksignal. The CPU 301 detects a failure in the color laser scanner unitsbased on whether or not each the scanner motor for the laser scannerunits 103 y, 103 m, 103 c, and 103 k outputs the lock signals.

In S1204, the CPU 301 determines whether or not the color high-voltageunits have a failure. The color high-voltage units correspond tohigh-voltage units (for yellow, magenta, and cyan) 275 configured toapply the primary transfer voltages to the primary transfer roller 105 yof the image forming station 120 y for yellow, the primary transferroller 105 m of the image forming station 120 m for magenta, and theprimary transfer roller 105 c of the image forming station 120 c forcyan, respectively. When there is a high-voltage unit having a failurein the high-voltage units (for yellow, magenta, and cyan) 275, the CPU301 determines that the high-voltage unit has a failure, and proceedsthe processing to S1207. On the contrary, when no high-voltage unit hasa failure, the CPU 301 determines that no high-voltage unit has afailure, and proceeds the processing to S1205. The CPU 301 detects afailure in each color high-voltage unit based on current value detectedat the time of application of the primary transfer voltage by adetecting portion configured to detect a current flowing to each primarytransfer roller 105.

In S1205, the CPU 301 determines whether or not the color drum motorshave a failure. The color drum motors correspond to the drum motor yconfigured to drive the photosensitive drum 101 y of the image formingstation 120 y for yellow, the drum motor m configured to drive thephotosensitive drum 101 m of the image forming station 120 m formagenta, and the drum motor c configured to drive the photosensitivedrum 101 c of the image forming station 120 c for cyan. When there is adrum motor having a failure in the drum motors y, m, and c, the CPU 301determines that the color drum motor has a failure, and proceeds theprocessing to S1207. On the contrary, when no drum motor has a failure,the CPU 301 determines that no color drum motor has a failure, andproceeds the processing to S1206.

In S1206, the CPU 301 stores, in the RAM 303, information indicatingthat the print restricted operation is not necessary, and terminates theprocessing. In S1207, the CPU 301 stores, in the RAM 303, informationindicating that the print restricted operation is necessary, andterminates the processing. The components subjected to theabove-mentioned print restricted operation are examples, and the presentinvention is not limited to the configuration described above.

<Control for Image Forming Apparatus in accordance with Color Mode>

[Setting of Color Mode]

FIG. 4A is a front view of the operating portion 330 according to thisembodiment. A start key 306 for starting the copy operation, a stop key307 for stopping the copy operation, and a numerical keypad 313 forsetting the digit entries are arranged on the operating portion 330. Adisplay portion 311 including a touch panel is arranged on the left ofthe operating portion 330. On a screen of the display portion 311, softkeys can be created. When a “COLOR/MONOCHROMATIC” key 318 displayed onthe display portion 311 is pressed, the screen illustrated in FIG. 4B ispopped up on the display portion 311. Thus, setting of a color mode fora printing or scanning operation of the image forming apparatus can beperformed. FIG. 4B is an illustration of a pop-up setting screenconfigured to enable setting of the color mode for the printing orscanning operation. When a key operation is performed with respect tothe display screen illustrated in FIG. 4B, setting of the color mode forthe printing or scanning operation is performed. The color mode isdesignated through a “FULL COLOR” key 321 for designation of the fullcolor mode, a “MONOCHROMATIC” key 322 for designation of themonochromatic mode, and an “AUTOMATIC” key 323 enabling the imageforming apparatus to make determination and decision to set the fullcolor mode or the monochromatic mode. When any one of those keys isselected, and an “OK” key 328 is pressed, setting of the color mode forthe printing or scanning operation is performed.

Setting can be performed through the “FULL COLOR” key 321 and the“AUTOMATIC” key 323 even under the print restricted operation state inwhich the print operation cannot be performed in the full color mode.This is because, when the setting of the color mode is not permittedduring the print restricted operation, processing of reading a colororiginal cannot be performed in a case where the original scanningoperation is to be performed through an original reading device (reader)being an input unit.

The CPU 301 can obtain a set value which is set through the operationunit 330, and the set value is stored in the RAM 303. Further, when theoperation to the operation unit 330 is detected, or when the placementof an original on the original table 152 is detected by the originalpresence sensor 151, the CPU 301 performs the print preparationoperation control in accordance with color mode setting stored in theRAM 303. Further, also when completion of initialization processing,which is performed at the time of power-on or restoration from the powersaving mode, is detected, the CPU 301 performs the print preparationoperation control in accordance with the color mode setting stored inthe RAM 303. In this embodiment, the color mode is set through operationto the color mode setting keys through the operation unit 330. However,for example, the color mode setting may be input from the externalcomputer 283 through the external I/F 282.

In this embodiment, as the print preparation operation, the temperatureof the fixing device 170 is shifted to a predetermined temperature inaccordance with the color mode setting, and the abutment and separationstates of the intermediate transfer belt unit 140 are switched inaccordance with the color mode setting. Details thereof are describedlater.

[Switching Control for Abutment and Separation Mechanism in Accordancewith Color Mode]

Description is made of the abutment and separation mechanism of thisembodiment being a switching unit, which is configured to switch theabutment and separation states of the intermediate transfer belt 130 andthe photosensitive drum 101 in the full color mode and the monochromaticmode.

(Description of Configurations of Photosensitive Drum and IntermediateTransfer Belt)

FIG. 5A and FIG. 5B are sectional views of the vicinity of theintermediate transfer belt unit 140 to which this embodiment is applied.As illustrated in FIG. 5A, the intermediate transfer belt 130 isstretched around five rollers including a drive roller 201, an idlerroller 202, a secondary transfer inner roller 203, a tension roller 204,and an auxiliary roller 205. Those rollers are driven by a motor (notshown) for the intermediate transfer belt to rotate, and theintermediate transfer belt 130 is driven by rotation of the rollers torotate. The drive roller 201, the idler roller 202, and the secondarytransfer inner roller 203 are supported on a frame 206 of theintermediate transfer belt unit 140 so as to be rotatable. The tensionroller 204 is supported by a bearing 207, which is movable in adirection indicated by the arrow C in FIG. 5A with respect to the frame206, in the vicinity of both ends of the tension roller 204 so as to berotatable. The bearing 207 is urged in a movable direction (thedirection indicated by the arrow C in FIG. 5A) by a spring 208, and theintermediate transfer belt 130 is stretched at a constant tension. On aninner side of the intermediate transfer belt unit 140, there arearranged the primary transfer rollers 105 which are opposed to thephotosensitive drums 101 with the intermediate transfer belt 130 beingdisposed therebetween. Both ends of each of the primary transfer rollers105 are supported by a bearing 210 so as to be rotatable. The bearing210 is guided by the frame 206 so as to be movable in one direction(up-and-down direction in FIG. 5A), and is urged by a spring 209 towardthe photosensitive drum 101. The photosensitive drums 101 are driven bythe drum motors 273 which are arranged so as to correspond to thephotosensitive drums 101, respectively.

FIG. 5A is a sectional view of the vicinity of the intermediate transferbelt unit 140 in the case where the full color mode is set as the colormode. FIG. 5B is a sectional view of the vicinity of the intermediatetransfer belt unit 140 in the case where the monochromatic mode is setas the color mode. When the full color mode is set, image formationusing toner of all colors is required. Thus, all of the primary transferrollers 105 y, 105 m, 105 c, and 105 k are brought into abutment againstthe opposed photosensitive drums 101 y, 101 m, 101 c, and 101 k throughintermediation of the intermediate transfer belt 130. The stateillustrated in FIG. 5A is hereinafter referred to as “abutment mode”.

When the monochromatic mode is set as the color mode, image formationusing only the black toner is performed. Thus, the photosensitive drum101 k for black and the primary transfer roller 105 k opposed theretoare brought into abutment against each other through intermediation ofthe intermediate transfer belt 130. Other primary transfer rollers 105y, 105 m, and 105 c are separated from the intermediate transfer belt130 and the opposed photosensitive drums 101 y, 101 m, and 101 c. Thedrum motors, which are configured to drive the photosensitive drums 101y, 101 m, and 101 c being separated, are stopped. As illustrated in FIG.5B, the primary transfer roller 105 y for yellow, the primary transferroller 105 m for magenta, the primary transfer roller 105 c for cyan,and the auxiliary roller 205 are retreated upward in FIG. 5B, and arebrought into a separation state of not being held in abutment againstthe intermediate transfer belt 130. The intermediate transfer belt 130is not even held in abutment against the photosensitive drum 101 y foryellow, the photosensitive drum 101 m for magenta, and thephotosensitive drum 101 c for cyan. Only the primary transfer roller 105k for black is held in abutment against the photosensitive drum 101 kfor black through intermediation of the intermediate transfer belt 130.The state illustrated in FIG. 5B is hereinafter referred to as“separation mode”.

(Configuration of Abutment and Separation Switching Mechanism andControl Therefor)

Next, with reference to FIG. 6A, FIG. 6B, FIG. 7A to FIG. 7E, FIG. 8A,and FIG. 8B, a switching mechanism configured to switch between theabutment mode and the separation mode is specifically described. FIG. 6Aand FIG. 6B are sectional views for illustrating an abutment andseparation mechanism 400 as viewed from a front side of the intermediatetransfer belt unit 140 illustrated in FIG. 5A and FIG. 5B. The abutmentand separation mechanism 400 is arranged inside the intermediatetransfer belt unit 140 to perform switching between the abutment modeand the separation mode. Further, the abutment and separation mechanism400 performs switching between the abutment mode and the separation modethrough sliding of a slider 402 in a horizontal direction(right-and-left direction in FIG. 6A and FIG. 6B). FIG. 6A is anillustration of a state before sliding of the slider 402, that is, astate in the abutment mode. FIG. 6B is an illustration of a state aftersliding of the slider 402 in the direction indicated by the arrow A inFIG. 6B, that is, a state in the separation mode. Actions of the slider402 at the time of sliding are described later.

The abutment and separation mechanism 400 is described with reference toFIG. 6A. A slide lever 401 is fixedly connected to the slider 402.Bearings 210 a, 210 y, 210 m, and 210 c are support portions configuredto support both ends of each of the auxiliary roller 205, the primarytransfer roller 105 y for yellow, the primary transfer roller 105 m formagenta, and the primary transfer roller 105 c for cyan, respectively soas to be rotatable. Lift arms 404 a, 404 y, 404 m, and 404 c areconfigured to support, from a lower side in FIG. 6A, the bearing 210 afor the auxiliary roller 205, the bearing 210 y for the primary transferroller 105 y, the bearing 210 m for the primary transfer roller 105 m,and the bearing 210 c for the primary transfer roller 105 c,respectively. Further, the lift arms 404 a, 404 y, 404 m, and 404 c aresupported in a rotatable state by bearings 403 a, 403 y, 403 m, and 403c, respectively, which are connection portions with respect to theslider 402. Further, there are arranged lift arm support portions 405 a,405 y, 405 m, and 405 c serving as fulcrums for rotation of the liftarms 404 a, 404 y, 404 m, and 404 c.

FIG. 7A to FIG. 7E are explanatory views for illustrating a cammechanism configured to slide the slider 402 of FIG. 6A and FIG. 6B inthe horizontal direction (right-and-left direction in FIG. 6A and FIG.6B). In FIG. 7A, a cam gear 502 and a cam portion 503 are fixed to ashaft 501. When the shaft 501 is rotated in the direction indicated bythe arrow in FIG. 7A, the cam gear 502 and the cam portion 503 are alsorotated in the direction indicated by the arrow in FIG. 7A along withthe rotation of the shaft 501. The slide lever 401 fixedly connected tothe slider 402 is arranged in contact with the cam portion 503 of thecam gear 502. FIG. 7A is an illustration of a state in which the camportion 503 does not interfere with the slide lever 401. That is, FIG.7A is an illustration of a state in which the cam portion 503 does notpress the slide lever 401 rightward in FIG. 7A, and is also anillustration of the state of the abutment and separation mechanism 400of FIG. 6A. In FIG. 6A, as compared to FIG. 6B, the bearings 210 a, 210y, 210 m, and 210 c are positioned on a lower side, and the primarytransfer roller 105 y for yellow, the primary transfer roller 105 m formagenta, the primary transfer roller 105 c for cyan, and the auxiliaryroller 205 are also positioned on a lower side. That is, FIG. 6A is anillustration of the abutment mode under the abutment state in which theprimary transfer rollers 105 y, 105 m, and 105 c are held in contactwith the intermediate transfer belt 130.

FIG. 8A and FIG. 8B are top views for illustrating the cam gear 502, thecam portion 503, and the shaft 501 illustrated in FIG. 7A to FIG. 7E asviewed from an upper side of FIG. 7A to FIG. 7E. As illustrated in FIG.8A, the cam gear 502 and the cam portion 503 are fixed to the shaft 501.Further, a flag 601 configured to detect abutment and separation isfixed to the shaft 501. The flag 601 is rotated along with the rotationof the shaft 501. At positions opposed to the flag 601, there arearranged an abutment sensor 325 and a separation sensor 326 with theshaft 501 being disposed therebetween. The abutment sensor 325 and theseparation sensor 326 employ photo-interrupters configured to detect thepresence or absence of an object through blocking of a light beam. Thatis, the abutment sensor 325 and the separation sensor 326 have the sameconfiguration, and are each configured to receive a light beam, which isemitted from a light emitting portion arranged on one wall portion alongwhich the flag 601 passes, at a light receiving portion, which isarranged on another wall portion. The abutment sensor 325 and theseparation sensor 326 are configured to detect changes in twolight-receiving states including a light-receiving state and alight-blocking state. In the light-receiving state, the light beamemitted from the light emitting portion can be received at the lightreceiving portion. In the light-blocking state, the light beam isblocked by the flag 601 and cannot be received at the light receivingportion. For example, FIG. 8A is an illustration of the state of FIG.7A. In FIG. 8A, the flag 601 blocks the light in the abutment sensor325. Thus, it can be determined that the abutment and separationmechanism 400 is in the abutment state (abutment mode). At this time,the flag 601 does not block the light in the separation sensor 326.Thus, the light beam emitted from the light emitting portion can bereceived at the light receiving portion, and thus it is not determinedthat the abutment and separation mechanism 400 is in the separationstate (separation mode).

Description is made of an operation which is performed when an abutmentand separation motor (not shown) configured to drive the abutment andseparation mechanism 400 is driven. Through driving of the abutment andseparation motor (not shown), the shaft 501 illustrated in FIG. 7A isrotated, and the cam gear 502 is rotated in the direction indicated bythe arrow (clockwise direction) along with the rotation of the shaft501. In FIG. 7B, the rotation of the cam gear 502 causes the cam portion503 to push the slide lever 401 in the direction indicated by the arrowA. FIG. 7C is an illustration of a state after rotation of the camportion 503 by 180° from FIG. 7A. At this time, the slide lever 401 ispushed at most in the direction indicated by the arrow A. The slidelever 401 is fixedly connected to the slider 402. Thus, in FIG. 7C, theslider 402 is pushed at most in the direction indicated by the arrow A.

FIG. 6B is an illustration of the state of the abutment and separationmechanism 400 at the above-mentioned timing. In FIG. 6B, portions areillustrated with the solid lines and the broken lines for comparison. Astate of the portions illustrated with the broken lines corresponds tothe state illustrated in FIG. 6A (abutment mode), and a state of theportions illustrated with the solid lines corresponds to an originalstate of FIG. 6B. In FIG. 6B, with the movement of the slider 402 in thedirection indicated by the arrow A as a point of action, and the liftarm support portions 405 a, 405 y, 405 m, and 405 c as fulcrums, thelift arms 404 a, 404 y, 404 m, and 404 c are rotated in the clockwisedirection from the state of the broken lines to the state of the solidlines. With this, the bearings 210 a, 210 y, 210 m, and 210 crespectively supported by ends of the lift arms 404 a, 404 y, 404 m, and404 c are pushed upward in the direction indicated by the arrow B inFIG. 6B. When the bearings 210 a, 210 y, 210 m, and 210 c are pushedupward, the primary transfer rollers 105 y, 105 m, and 105 c which arerespectively supported by the bearings 210 y, 210 m, and 210 c are alsopushed upward. As a result, the primary transfer rollers 105 y, 105 m,and 105 c are brought into the separation state (separation mode) of notbeing held in contact with the intermediate transfer belt 130. FIG. 8Bis an illustration of the state of the flag 601 at that timing. In FIG.8B, the flag 601 blocks the light in the separation sensor 326, and itcan be determined that the abutment and separation mechanism 400 is inthe separation state (separation mode). At this time, the flag 601 doesnot block the light in the abutment sensor 325, and the light beamemitted from the light emitting portion is received at the lightreceiving portion. Thus, it is not determined that the abutment andseparation mechanism 400 is in the abutment state (abutment mode). Theabove-mentioned method and configuration for the abutment and separationdetection are examples, and thus the present invention is not limited tothe above-mentioned configuration. For example, the separation state maybe achieved through movement of the photosensitive drums 101 withrespect to the intermediate transfer belt 130, or through movement ofboth the photosensitive drums 101 and the intermediate transfer belt130.

When the abutment and separation motor is driven from the state of FIG.7C to rotate the cam gear 502 in the direction indicated by the arrow(clockwise direction), as illustrated in FIG. 7D, the slide lever 401having been pushed by the cam portion 503 slides in the directionindicated by the arrow D. The slide lever 401 slides in the directionindicated by the arrow D, which is a direction reverse to the directionindicated by the arrow A. At last, the slide lever 401 returns to aninitial position as illustrated in FIG. 7E, that is, returns to theabutment state (abutment mode) illustrated in FIG. 6A. Theabove-mentioned configuration of the abutment and separation mechanism400 is an example, and the present invention is not limited to theabove-mentioned configuration.

When the color mode is in the monochromatic mode, the abutment andseparation mechanism 400 is set to the separation mode, thereby beingcapable of reducing abrasion of the surfaces of the photosensitive drums101 y, 101 m, and 101 c due to friction with the intermediate transferbelt 130. With this, as compared to the case of not being separated, thelifetime limit of the photosensitive drums 101 y, 101 m, and 101 c canbe extended. Further, along with the separation, the drum motors (notshown) configured to drive the photosensitive drums 101 y, 101 m, and101 c can also be stopped, thereby being capable of achieving powersaving.

At the time of print standby, the image forming apparatus according tothis embodiment is set to standby under a state in which theintermediate transfer belt unit 140 is separated (state in theseparation mode). Thus, when the image formation is completed, or whenthe print preparation operation is performed but timeout occurs due tono input of a job for a predetermined period of time, the state isshifted to the state of the separation mode. Therefore, when the imageformation is to be performed in the full color mode, it is necessary toshift the intermediate transfer belt unit 140 to the state of theabutment mode before starting the image formation. In this embodiment,the intermediate transfer belt unit 140 is shifted to the abutment modeor to the separation mode during the print preparation operation priorto the print operation. With this, the time for switching of theabutment and separation modes before the start of the image formation isreduced, thereby being capable of shortening the first copy output time.

Even when the abutment and separation state at the time of print standbyis any one of the state in the separation mode or the state of retainingthe state in the abutment mode for the image formation, time forswitching the abutment and separation modes is required before the printoperation is to be performed in a different mode. In this embodiment,the abutment and separation modes are switched prior to the printoperation, and it is not limited to the abutment and separation statesat the time of print standby.

[Adjustment Control for Temperature of Fixing Device]

Description is made of an adjustment control for a fixing temperature ofthe fixing device 170 in the full color mode and in the monochromaticmode in this embodiment.

(Configuration of Fixing Device)

FIG. 9 is a sectional view of the fixing device 170 being a fixing unitconfigured to fix an unfixed toner image T, which has been transferredonto a recording material by the secondary transfer portion 118, on arecording material P. In FIG. 9, the fixing device 170 includes a fixingfilm 6, a pressure roller 9, a heater 1, and a thermistor 5. The fixingfilm 6 is a fixing body formed of a cylindrical metal member. Thethermistor 5 is a temperature detector. The pressure roller 9 is drivenby a fixing drive motor (not shown) to rotate. The pressure roller 9 isarranged at a position opposed to the heater 1 with the fixing film 6being disposed therebetween, and is brought into press contact with alower surface of the heater 1 by an urging spring (not shown) at apressing force of, for example, from 5 kgf to 20 kgf. The fixing film 6is driven in the direction indicated by the arrow (counterclockwisedirection) which is a forward direction with respect to a conveyingdirection of the recording material P along with the rotation of thepressure roller 9 in the direction indicated by the arrow (clockwisedirection).

The fixing film 6 forms a fixing nip portion with the pressure roller 9.The heater 1 is arranged to heat the recording material P which passesthrough the fixing nip portion. The heater 1 receives supply of power atboth ends thereof in the longitudinal direction (direction perpendicularto the drawing sheet of FIG. 9). An alternate-current voltage applied tothe heater 1 is AC 100 V, and the heater 1 generates heat with theapplied voltage. The thermistor 5 configured to detect the temperatureof the heater 1 is arranged in the vicinity of a center portion of theheater 1 in the longitudinal direction. At the time of image formation,the CPU 301 performs a control for supply of power to the heater 1 sothat a detected temperature by the thermistor 5 reaches a predeterminedtarget temperature. When the recording material P bearing the unfixedtoner image T is introduced to the fixing nip portion formed between thefixing film 6 and the pressure roller 9, the recording material P isconveyed while being heated by the heater 1 and receiving the pressurefrom the pressure roller 9. With this, the unfixed toner image T isfixed to the recording material P.

(Fixing Temperature Adjustment Control During Print PreparationOperation)

A temperature adjustment control for the fixing device 170 during theprint preparation operation is described with reference to FIG. 10A toFIG. 10D. FIG. 10A is a timing chart for illustrating a relationshipbetween detected temperatures by the thermistor 5 and supply of power tothe heater 1 at the start of the print preparation operation and at thestart of the print operation in the fixing device 170. FIG. 10B is atable for showing print preparation temperatures, which are targettemperatures during the print preparation operation, and a printtemperature, which is a target temperature during the print operation,in a case where the full color mode or the monochromatic mode isdesignated as the color mode. In this embodiment, the temperature of thefixing device 170 is set to optimum target temperatures during the printpreparation operation and the print operation in accordance with thecolor mode set by input through the operation unit 330. In FIG. 10B, theprint preparation temperature, which is the target temperature duringthe print preparation operation, is 80° C. being a first temperature inthe case where the full color mode is set as the color mode, and theprint preparation temperature is 120° C. being a second temperature inthe case where the monochromatic mode is set. The print temperature,which is the target temperature in the case of starting the printoperation, is 150° C. being a third temperature in the case where thecolor mode is any one of the full color mode or the monochromatic mode.

With reference to FIG. 10A, the temperature adjustment for the fixingdevice 170 during the print preparation operation and the printoperation is described. FIG. 10A is a graph (upper graph) for showingchanges in temperature of the heater 1 of the fixing device 170 and atiming chart (lower timing chart) for illustrating states of supply ofpower to the heater 1, during the print preparation operation and theprint operation. In the upper graph, the horizontal axis representstime, and the vertical axis represents the temperature of the heater 1(fixing temperature in FIG. 10A). In the lower timing chart, thehorizontal axis represents time, and the vertical axis represents power(fixing power in FIG. 10A) supplied to the heater 1. In FIG. 10A, thetimes T1, T2, T2 m, T3, T4 m, and T4 represent timings. The time T1represents a timing of starting the print preparation operation. Thetime T3 represents a timing of starting the print operation. In FIG.10A, the thick solid lines represent the state in which the color modeis the full color mode, and the broken lines represent the state inwhich the color mode is the monochromatic mode.

Description is made of the temperature adjustment for the fixing device170 in the case where the color mode set through the operation unit 330is the full color mode. At the time T1 of starting the print preparationoperation, the CPU 301 performs supply of power of 1,000 W to the heater1 until the detected temperature of the heater 1 by the thermistor 5reaches 80° C. being the print preparation temperature in the case ofthe full color mode. Then, at the time T2, when the detected temperatureby the thermistor 5 becomes equal to or higher than 80° C. being theprint preparation temperature, the CPU 301 switches the supply of powerto the heater 1 from 1,000 W to 300 W so that the detected temperatureby the thermistor 5 is maintained at 80° C. being the print preparationtemperature. The time T2 at which the detected temperature by thethermistor 5 becomes equal to or higher than 80° C. being the printpreparation temperature is changed in accordance with the detectedtemperature by the thermistor 5 at the time T1.

FIG. 10C is a table for showing a relationship of a temperaturedifference, which is between the print preparation temperature and thedetected temperature by the thermistor 5 at the time T1, with respect totime ta (=time T2−time T1) which is required to reach the printpreparation temperature. For example, when the detected temperature bythe thermistor 5 is 30° C. at the time T1, and in the case of the fullcolor mode where the print preparation temperature is 80° C., the timeta required to raise the temperature by 50° C. (=80° C.−30° C.) to reach80° C. is 8 seconds according to the value shown in the table. When thedetected temperature by the thermistor 5 is 90° C. at the time T1, thetemperature is already higher than 80° C. being the print preparationtemperature for the case of the full color mode. Thus, the time ta is 0seconds according to the value shown in the table. The data of the tableshown in FIG. 10C is obtained in advance through experiment.

Next, from the time T3 of starting the print operation, the CPU 301performs the supply of power of 1,000 W to the heater 1 until thedetected temperature of the heater 1 by the thermistor 5 reaches 150° C.being the print temperature of fixing the unfixed toner image on therecording material P. At the time T4 at which the detected temperatureby the thermistor 5 reaches 150° C. being the print temperature, and therecording material P having the unfixed toner image formed thereonarrives at the fixing device 170, the CPU 301 switches the supply ofpower to the heater 1 from 1,000 W to 600 W. That is, the CPU 301switches the supply of power to the heater 1 from 1,000 W to 600 W sothat the detected temperature by the thermistor 5 is maintained at 150°C. being the print temperature, thereby fixing the unfixed toner image Ton the recording material P.

Description is made of the temperature adjustment for the fixing device170 in the case where the color mode is the monochromatic mode, or inthe case where the color mode is an automatic determination mode ofsetting the full color mode or the monochromatic mode based on whetheror not an image of an original read by the image sensor 233 is amonochromatic image (based on property of an image). From the time T1 ofstarting the print preparation operation, the CPU 301 performs supply ofpower of 1,000 W to the heater 1 until the detected temperature of theheater 1 by the thermistor 5 reaches 120° C. being the print preparationtemperature for the case of the monochromatic mode. Then, at the time T2m, when the detected temperature by the thermistor 5 is equal to orhigher than 120° C. being the print preparation temperature, the CPU 301switches the supply of power to the heater 1 from 1,000 W to 400 W sothat the detected temperature by the thermistor 5 is maintained at 120°C. being the print preparation temperature. The time T2 m at which thedetected temperature by the thermistor 5 becomes equal to or higher than120° C. being the print preparation temperature is changed in accordancewith the detected temperature by the thermistor 5 at the time t1.

Next, at the time T3 of starting the print operation, the CPU 301performs supply of power of 1,000 W to the heater 1 until the detectedtemperature of the heater by the thermistor 5 reaches 150° C. being theprint temperature of fixing the unfixed toner image on the recordingmaterial P. At the time T4 m at which the detected temperature by thethermistor 5 reaches 150° C. being the print temperature and at whichthe recording material P having the unfixed toner image formed thereonarrives at the fixing device 170, the CPU 301 switches the supply ofpower to the heater 1 from 1,000 W to 600 W. That is, the CPU 301switches the supply of power to the heater 1 from 1,000 W to 600 W sothat the detected temperature by the thermistor 5 is maintained at 150°C. being the print temperature, thereby fixing the unfixed toner image Ton the recording material P.

In order to fix the unfixed toner image T on the recording material P,the print preparation temperature is set so that the detectedtemperature of the heater 1 by the thermistor 5 becomes equal to orhigher than 150° C. at the time T4 at which the recording material Parrives at the fixing device 170. As the print preparation temperatureis set higher, the temperature of the heater 1 can reach 150° C. beingthe print temperature earlier after the start of the print operation.However, as the print preparation temperature is set higher, more powerneeds to be supplied to maintain the heater 1 at the print preparationtemperature, which is not efficient in terms of power saving. Therefore,in this embodiment, in accordance with the color mode set through theoperation unit 330, the setting of the print preparation temperature isdifferent between the case where the color mode is the full color modeand the case where the color mode is the monochromatic mode. With this,the temperature of the fixing device 170 reaches 150° C. being the printtemperature at the time T4 (or time T4 m), thereby being capable ofshortening the first copy output time, which is the time required tooutput a first copy, and achieving power saving.

Description is made of a difference in setting of the print preparationtemperature between the case where the color mode is the full color modeand the case where the color mode is the monochromatic mode. FIG. 10D isa sectional view of the vicinity of the intermediate transfer belt unit140 and the secondary transfer portion 118. The view on the upper sideis a sectional view for illustrating the case where the monochromaticmode is set as the color mode. The view on the lower side is a sectionalview for illustrating the case where the full color mode is set as thecolor mode. In the view on the upper side of FIG. 10D, a distanceDistMono indicated by the thick solid line represents a distancerequired for the recording material P to proceed from when the imageforming station 120 k for black starts image formation to when therecording material P having a black toner image T transferred thereonreaches the fixing device 170. In the view on the lower side of FIG.10D, a distance DistFull indicated by the thick solid line represents adistance required for the recording material P to proceed from when theimage forming station 120 y for yellow starts image formation to whenthe recording material P having a yellow toner image T transferredthereon reaches the fixing device 170. As is apparent from FIG. 10D, thetwo distances DistMono and DistFull satisfy a relationship of distanceDistFull>distance DistMono. The speed of image formation is equal in themonochromatic printing and the full color printing. Thus, the distancerelationship and a time relationship from the start of image formationto the arrival of the recording material P at the fixing device 170 aresimilar. That is, time TsFull required for the recording material P toreach the fixing device 170 in the full color mode and time TsMonorequired for the recording material P to reach the fixing device 170 inthe monochromatic mode satisfy a relationship of time TsFull>timeTsMono.

Therefore, a time period of supplying power to the heater 1 from thestart of the image formation by the image forming unit 120 to thearrival of the recording material P at the fixing device 170 is longerin the full color mode than the monochromatic mode. The printtemperature of the fixing device 170 is equal in the monochromatic modeand the full color mode. Therefore, the print preparation temperaturebeing the temperature of the fixing device 170 at the time of startingthe print operation can be set lower in the case of the full color modethan the case of the monochromatic mode. As compared to the case of notswitching the print preparation temperature in accordance with the colormode, in this embodiment, the print preparation temperature can be setlower in the case where the color mode is the full color mode. Withthis, the supply of power for maintaining the print preparationtemperature can be set smaller, thereby being effective in terms ofpower saving. The print preparation temperature and the supply of powerare set to fixed values in this embodiment, but may be changed inaccordance with, for example, an environmental temperature or a powersupply voltage.

(Control for Abutment and Separation Mechanism During Print PreparationOperation)

Description is made of a control for the abutment and separationmechanism 400 during the print preparation operation. In thisembodiment, the state of the abutment and separation mechanism 400 isswitched during the print preparation operation in accordance with thecolor mode setting which is set through the operation unit 330. At thistime, when the full color mode is set as the color mode, the printpreparation operation is performed so as to bring the abutment andseparation mechanism 400 into the state of the abutment mode. When theautomatic determination mode (third mode) is set, the print preparationoperation is performed so as to bring the abutment and separationmechanism 400 into the separation mode. In the automatic determinationmode, any one of the full color mode and the monochromatic mode isautomatically set as the color mode based on a property of an inputimage. When the automatic determination mode is set, the same printpreparation operation as the monochromatic mode is performed. Such aconfiguration is employed because of the following reason. In the caseof the automatic determination mode, the color mode is not determineduntil printing is started. Thus, it is necessary to perform the printpreparation operation with prediction of the color mode. Accordingly,improvement in the first copy output time can be expected when the printpreparation operation is performed in the monochromatic mode which isfrequently used.

Comparative Embodiment

(Control Sequence for Print Preparation Operation)

Now, a comparative embodiment is described with reference to FIG. 11.FIG. 11 is a flowchart for illustrating a control sequence for the printpreparation operation, and the control sequence is executed by the CPU301. The processing of FIG. 11 is started upon detection of a printprediction operation from which a subsequent print operation startinstruction is predicted, that is, upon detection of the opening andclosing operations of the original pressure plate or the placement of anoriginal on the original table 152 through the original feeder controlportion 480 or the image reader control portion 280, or upon detectionof an operation to the operation unit 330. In the comparativeembodiment, during the print restricted operation, the print preparationoperation is not performed in the full color mode, and the printpreparation operation in the monochromatic mode is performed.

In S1001, the CPU 301 resets and starts a timer 291 to monitor whetheror not a print operation start instruction is given within apredetermined time period. The timer 291 adds a timer value every 1millisecond (ms), and the CPU 301 refers to the timer value of the timer291 to determine an elapsed time from the start of the timer 291 inS1001. In S1002, the CPU 301 reads the color mode setting stored in theRAM 303 to determine whether or not the set color mode is the full colormode. When it is determined that the set color mode is the full colormode, the CPU 301 proceeds the processing to S1003. When it isdetermined that the set color mode is not the full color mode, that is,the set color mode is the monochromatic mode or the automaticdetermination mode, the CPU 301 proceeds the processing to S1007.

In S1003, in order to determine whether or not the full color printrestricted operation is necessary, the CPU 301 starts the processing ofdetermining the necessity of the full color print restricted operationdescribed with reference to FIG. 3. In S1004, the CPU 301 reads a resultof the processing of S1003 from the RAM 303 to determine whether or notthe full color print restricted operation is unnecessary. When it isdetermined that the full color print restricted operation isunnecessary, the CPU 301 proceeds the processing to S1005. When it isdetermined that the full color print restricted operation is necessary,the CPU 301 proceeds the processing to S1007.

In S1005, the CPU 301 sets the color mode of the print preparationoperation to the full color mode. In S1006, the CPU 301 sets the printpreparation temperature of the fixing device 170 to 80° C. being theprint preparation temperature for the full color mode (print preparationtemperature=full color print preparation temperature), performs supplyof power to the heater 1 of the fixing device 170, and proceeds theprocessing to S1009.

In the case of NO in S1002, the color mode set through the operationunit 330 is the monochromatic mode or the automatic determination mode.Thus, in S1007, the CPU 301 sets the color mode for the printpreparation operation to the monochromatic mode. Further, when the printrestricted operation is to be performed (NO in S1004), the CPU 301 setsthe color mode for the print preparation operation to the monochromaticmode irrespective of the color mode setting which is set through theoperation unit 330. In S1008, the CPU 301 sets the print preparationtemperature of the fixing device 170 to 120° C. being the printpreparation temperature for the monochromatic mode (print preparationtemperature=monochromatic print preparation temperature), performssupply of power to the heater 1 of the fixing device 170, and proceedsthe processing to S1009.

In S1009, the CPU 301 performs the control for the abutment andseparation mechanism 400 in accordance with the color mode setting forthe print preparation operation. The control for the abutment andseparation mechanism 400 is executed in the subroutine, and detailsthereof are described later.

In S1010, the CPU 301 determines whether or not the print operationstart instruction from the operation unit 330 is detected (in FIG. 11,“PRINT OPERATION START INSTRUCTION IS GIVEN”). When it is determinedthat the print operation start instruction is detected, the CPU 301terminates the processing. When it is determined that the printoperation start instruction is not detected, the CPU 301 proceeds theprocessing to S1013.

In S1013, the CPU 301 refers to the timer value of the timer 291 todetermine whether or not 15 seconds or more have elapsed. When it isdetermined that 15 seconds or more have elapsed, the CPU 301 proceedsthe processing to S1014. When the elapsed time is less than 15 seconds,the CPU 301 proceeds the processing to S1016. The time of 15 seconds isan example of a waiting time from the print prediction operation, fromwhich the print operation start instruction is predicted, to detectionof the print operation start instruction, and the time is not limited to15 seconds. In S1014, the CPU 301 stops the supply of power to theheater 1 of the fixing device 170. In S1015, the CPU 301 controls theabutment and separation mechanism 400 to the state of the separationmode, and terminates the processing.

In S1016, the CPU 301 determines whether or not an operation of pressinga key or other operation is performed to the operation unit 330. Whenthe operation is performed, the CPU 301 returns the processing to S1001.When the operation is not performed, the CPU 301 returns the processingto S1010.

When the print operation start instruction is detected, the CPU 301terminates the print preparation operation and starts the printoperation. Before the print operation is started, the CPU 301 checkswhether or not the state of the abutment and separation mechanism 400matches with the color mode setting given at the time of the print startinstruction. Then, when the state is unmatched with the color modesetting, the CPU 301 performs the control to achieve the state in whichthe abutment and separation mechanism 400 matches with the color mode.Such a configuration is employed because of the following reason. In thecase of the automatic determination mode, the abutment and separationmechanism 400 is in the state of separation to perform the printpreparation operation in the monochromatic mode. Thus, when a print jobof the full color mode is executed, the full color print operationcannot be performed in such a state.

In the comparative embodiment, when the print start instruction of thefull color mode is received during the print restricted operation, thefollowing processing is performed to notify that the full color printingcannot be performed. That is, the CPU 301 controls the display portion311 (notification unit) of the operation unit 330 to display a messageto confirm whether or not to perform the monochromatic printing (seeFIG. 4C). Then, the CPU 301 performs the monochromatic printing when auser presses the OK button 329. The print preparation operation in themonochromatic mode is completed in advance. Thus, when the user pressesthe OK button 329, the CPU 301 switches, at the time of startingprinting, the temperature of the fixing device 170 to 150° C. being theprint temperature, and starts the image forming operation.

(Control Sequence for Abutment and Separation Mechanism)

FIG. 12 is a flowchart for illustrating the subroutine of the controlsequence for the abutment and separation mechanism 400. The subroutineis started when the processing of S1009 of FIG. 11 is executed, and theprocessing is executed by the CPU 301. When the processing isterminated, the CPU 301 proceeds to the processing of S1010 of FIG. 11.

In S1101, the CPU 301 reads the color mode setting for the printpreparation operation to determine whether or not the set color mode isthe full color mode. When it is determined that the set color mode isthe full color mode, the CPU 301 proceeds the processing to S1102. Whenit is determined that the set color mode is not the full color mode,that is, the set color mode is the monochromatic mode, the CPU 301proceeds the processing to S1104. In S1102, the CPU 301 determineswhether or not the state of the abutment and separation mechanism 400 isthe separation state (separation mode). When it is determined that thestate of the abutment and separation mechanism 400 is the separationstate, the CPU 301 proceeds the processing to S1103. When it isdetermined that the state of the abutment and separation mechanism 400is not the separation state or is the abutment state, the CPU 301terminates the processing without changing the state of the abutment andseparation mechanism 400. In S1103, the CPU 301 shifts the state of theabutment and separation mechanism 400 to the abutment state (abutmentmode), and terminates the processing.

In S1104, the CPU 301 determines whether or not the state of theabutment and separation mechanism 400 is the abutment state (abutmentmode). When it is determined that the state of the abutment andseparation mechanism 400 is the abutment state, the CPU 301 proceeds theprocessing to S1105. When it is determined that the state of theabutment and separation mechanism 400 is not the abutment state or isthe separation state, the CPU 301 terminates the processing withoutchanging the state of the abutment and separation mechanism 400. InS1105, the CPU 301 shifts the state of the abutment and separationmechanism 400 to the separation state (separation mode), and terminatesthe processing.

In the comparative embodiment, the print preparation operation controlis switched in accordance with the color mode setting, thereby beingcapable of shortening the first copy output time. Further, when thecolor toner is used up, or during the print restricted operation inwhich only the monochromatic print operation can be performed due to afailure in a component which is used only for the full color printoperation, the full color print preparation operation control is notperformed, and the monochromatic print preparation operation isperformed. With this, the print preparation operation can optimally beperformed. As a result, an unnecessary operation is not performed duringthe print preparation operation, thereby being capable of achievingpower saving for drive power. Further, the abrasion of thephotosensitive drum due to the friction with the intermediate transferbelt is prevented, thereby being capable of extending the lifetime limitof the photosensitive drum.

Present Embodiment

In the comparative embodiment, the print preparation operation in themonochromatic mode is performed during the print restricted operation.However, in the case of the comparative embodiment, when only a scanningoperation is performed under a state in which a user sets the color modeto the full color mode through the operation unit 330 during the printrestricted operation, an unnecessary print preparation operation isperformed. In order to avoid such a circumstance, in this embodiment,the print preparation operation is not performed during the printrestricted operation when the instruction of the print preparationoperation in the full color mode is received.

(Control Sequence for Print Preparation Operation)

FIG. 13 is a flowchart for illustrating a control sequence for the printpreparation operation in the image forming apparatus according to thisembodiment, and the control sequence is executed by the CPU 301. Theprocessing of FIG. 13 is started upon detection of a print predictionoperation from which a subsequent print operation start instruction ispredicted, that is, upon detection of the opening and closing operationsof the original pressure plate or the placement of an original on theoriginal table 152 through the original feeder control portion 480 orthe image reader control portion 280, or upon detection of an operationto the operation unit 330. The processing of FIG. 13 is different fromthe processing of the comparative embodiment illustrated in FIG. 11 inthat the print preparation operation is not performed during the printrestricted operation.

In FIG. 13, the processing steps of S1301 to S1308 are the same as theprocessing steps of S1001 to S1008 of the comparative embodiment of FIG.11, except for the processing in the case of NO in S1304. Thus,description thereof is omitted. In S1304, the CPU 301 determines whetheror not the full color print restricted operation is unnecessary. When itis determined that the full color print restricted operation isunnecessary, the CPU 301 proceeds the processing to S1305. When it isdetermined that the full color print restricted operation is necessary,the CPU 301 proceeds the processing to S1310.

In S1309, the CPU 301 performs the following processing to indicate thatthe print preparation operation in the full color mode (S1305 and S1306)or the print preparation operation in the monochromatic mode (S1307 andS1308) is performed. That is, the CPU 301 turns on a print preparationoperation performance flag (hereinafter referred to as “performanceflag”), stores the performance flag in the RAM 303, and proceeds theprocessing to S1311. Meanwhile, in S1310, in order to indicate that theprint preparation operation is not performed, the CPU 301 turns off theperformance flag, stores the performance flag in the RAM 303, andproceeds the processing to S1312.

The processing of S1311 is the same as the processing of S1009 of FIG.11. Thus, description thereof is omitted. In S1312, the CPU 301determines whether or not the print operation start instruction from theoperation unit 330 is detected (in FIG. 13, “PRINT OPERATION STARTINSTRUCTION IS GIVEN”). When it is determined that the print operationstart instruction is detected, the CPU 301 terminates the processing.When it is determined that the print operation start instruction is notdetected, the CPU 301 proceeds the processing to S1313. In S1313, theCPU 301 reads the performance flag from the RAM 303 to determine whetheror not the performance flag is in an on-state. When it is determinedthat the performance flag is in the on-state, the CPU 301 proceeds theprocessing to S1314. When it is determined that the performance flag isnot in the on-state, or is in the off-state, the CPU 301 proceeds theprocessing to S1317. In S1314, the CPU 301 refers to the timer value ofthe timer 291 to determine whether or not 15 seconds or more haveelapsed. When it is determined that the 15 seconds or more have elapsed,the CPU 301 proceeds the processing to S1315. When the elapsed time isless than 15 seconds, the CPU 301 proceeds the processing to S1317. Thetime of 15 seconds is an example of a waiting time from the printprediction operation, from which the print operation start instructionis predicted, to detection of the print operation start instruction, andthe time is not limited to 15 seconds. The processing steps of S1315,S1316, and S1317 are the same as the processing steps of S1014, S1015,and S1016 of FIG. 11. Thus, description thereof is omitted.

When the print operation start instruction is detected, the CPU 301terminates the print preparation operation. Also in this embodiment,similarly to the comparative embodiment, the CPU 301 checks, beforestarting the print operation, whether or not the state of the abutmentand separation mechanism 400 matches with the color mode of the printstart instruction, that is, the state of the abutment and separationmechanism 400 matches with the color mode set in the RAM 303. When thestate of the abutment and separation mechanism 400 is unmatched with thecolor mode, the CPU 301 brings the abutment and separation mechanism 400into the state of matching with the color mode setting. Such aconfiguration is employed because of the following reason. In the caseof the automatic determination mode, the abutment and separationmechanism 400 is in the separation state to perform the printpreparation operation in the monochromatic mode. Thus, when a print jobof the full color mode is executed, the full color print operationcannot be performed in such a state.

In this embodiment, when the print start instruction of the full coloris received during the print restricted operation under the state inwhich the color mode setting is set to the full color mode, neither thefull color printing nor the monochromatic printing can be performed.Therefore, the CPU 301 controls the display portion 311 of the operationunit 330 to display a message to confirm whether or not to perform themonochromatic printing (see FIG. 4C). Then, when the user presses the OKbutton 329, in order to perform the monochromatic printing, the CPU 301supplies power so that the temperature of the fixing device 170 reaches150° C. being the print temperature at the time of starting printing,and thereafter starts the image forming operation.

In this case, the print preparation operation is not performed duringthe print restricted operation irrespective of the set color mode. Thus,the power is not supplied to the fixing device 170. Therefore, ascompared to the comparative embodiment in which the print preparationoperation in the monochromatic mode is performed in advance, the firstcopy output time becomes longer. When the scanning operation isperformed under a state in which the user sets the color mode setting tothe full color mode, the print preparation operation in themonochromatic mode is not performed in this embodiment, unlike thecomparative embodiment. Therefore, the abrasion of the photosensitivedrum 101 k for black is prevented, thereby being capable of extendingthe lifetime limit of the photosensitive drum 101 k.

In this embodiment, when the opening and closing of the originalpressure plate, the placement of an original on the original table 152,or the operation to the operation unit 330 is detected, the CPU 301performs the control for the print preparation operation. Operationsfrom which printing is expected include, for example, a mounting andremoving operation of the sheet feeding cassette 111, placement of asheet on the multi tray 117, print condition setting input from theexternal computer 283 through the external I/F 282, or detection of anapproach or a contact by a person through a human sensor. Therefore,those conditions may be added to the determination conditions in S1317of FIG. 13, and the CPU 301 may perform the print preparation operationwhen those operations, from which printing is expected, are detected. Inthis embodiment, description is made of the control for the abutment andseparation mechanism 400 and the control for the temperature adjustmentof the fixing device 170 as subjects to the print preparation operation.For example, as the subject to the print preparation operation, thecontrol for a startup operation for scanner motors (not shown), whichare driven when the laser scanner units 103 y, 103 m, 103 c, and 103 kirradiate laser light to corresponding photosensitive drums 101, may beperformed. In this case, when the print preparation operation isperformed during the print restricted operation, the startup operationis performed only for the scanner motor of the laser scanner unit 103 k,and the startup operation is not performed for the scanner motors ofother laser scanner units 103 y, 103 m, and 103 c.

As described above, according to this embodiment, the print preparationoperation control can be performed in accordance with the state of theimage forming unit.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2016-064112, filed Mar. 28, 2016, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An image forming apparatus, comprising: an imageforming unit including a plurality of image forming stations configuredto respectively perform image formation of different colors, the imageforming unit being configured to perform image formation on a recordingsheet in any one of a first mode, in which image formation is performedthrough use of the plurality of image forming stations, and a secondmode, in which image formation is performed through use of apredetermined image forming station among the plurality of image formingstations; an operation unit configured to allow input of color modeinformation for setting whether the image forming unit is to performimage formation in the first mode or to perform image formation in thesecond mode; and a controller configured to: i) control the imageforming unit to perform a preparation operation for image formation inaccordance with the color mode information before image formation whendetecting an operation from which a start instruction of image formationis predicted; ii) set a restricted operation state in which thecontroller prohibits performing the image formation in the first modeand permits performing the image formation in the second mode when anyone image forming station, except for the predetermined image formingstation, among the plurality of image forming stations is incapable ofperforming image formation, and the predetermined image forming stationis capable of performing image formation; and iii) prevent the imageforming unit from performing the preparation operation when the inputcolor mode information sets to perform the image formation in the firstmode, and the restricted operation state is set.
 2. An image formingapparatus according to claim 1, wherein, the controller terminates thepreparation operation if the start instruction is not input within apredetermined time period after the preparation operation is started. 3.An image forming apparatus according to claim 2, further comprising aninput unit configured to input an image to be formed, wherein the colormode information includes first instruction information for instructingthe image forming unit to perform the image formation in the first mode,second instruction information for instructing the image forming unit toperform the image formation in the second mode, and third instructioninformation different from the first instruction information and thesecond instruction information, and wherein, when the third instructioninformation is set as the color mode information, the controllerdetermines to perform the image formation in the first mode or thesecond mode based on a property of the input image.
 4. An image formingapparatus according to claim 3, wherein, when the image formingapparatus is in the restricted operation state, the first instructioninformation or the third instruction information is capable ofselectively being set as the color mode information, and the secondinstruction information is incapable of being set as the color modeinformation.
 5. An image forming apparatus according to claim 3, whereinthe input unit includes a reader configured to read an image of anoriginal, and wherein the operation from which the start instruction ispredicted includes an operation of placing the original on a tray of thereader.
 6. An image forming apparatus according to claim 5, wherein thereader includes a detector configured to detect a presence or absence ofthe original on the tray, and wherein the controller detects placementof the original on the tray based on a detection result of the detector.7. An image forming apparatus according to claim 3, wherein theoperation from which the start instruction is predicted includes anoperation of inputting the color mode information through the operationunit.
 8. An image forming apparatus according to claim 3, wherein eachof the plurality of image forming stations includes a photosensitivemember on which a toner image is formed, and an exposure unit configuredto expose the photosensitive member, wherein the exposure unit includesa rotary polygon mirror configured to deflect laser light from a lightsource to expose the photosensitive member, and a motor configured torotate the rotary polygon mirror, wherein, when the first instructioninformation is set as the color mode information, the controller causesthe rotary polygon mirrors of all of the plurality of image formingstations to rotate as the preparation operation, and wherein, when thesecond instruction information or the third instruction information isset as the color mode information, the controller causes the rotarypolygon mirror of the predetermined image forming station to rotate asthe preparation operation, and prevents the rotary polygon mirrors ofother image forming stations, except for the predetermined image formingstation, among the plurality of image forming stations from rotating. 9.An image forming apparatus according to claim 8, wherein the restrictedoperation state includes a state in which the rotary polygon mirrors ofthe other image forming stations, except for the predetermined imageforming station, among the plurality of image forming stations are notrotatable.
 10. An image forming apparatus according to claim 3, whereineach of the plurality of image forming stations includes aphotosensitive member on which a toner image is formed, wherein theimage forming unit includes: an intermediate transfer belt onto whichtoner images formed on the photosensitive members of the plurality ofimage forming stations are transferred; and a switching unit configuredto switch abutment and separation between the photosensitive members ofthe plurality of image forming stations and the intermediate transferbelt, wherein, when the first instruction information is set as thecolor mode information, the controller controls the switching unit asthe preparation operation so that the photosensitive members in all ofthe plurality of image forming stations are brought into an abutmentstate against the intermediate transfer belt, and wherein, when thesecond instruction information or the third instruction information isset as the color mode information, the controller controls the switchingunit as the preparation operation so that the photosensitive member ofthe predetermined image forming station is brought into an abutmentstate against the intermediate transfer belt, and that thephotosensitive members of other image forming stations, except for thepredetermined image forming station, among the plurality of imageforming stations are brought into a separation state from theintermediate transfer belt.
 11. An image forming apparatus according toclaim 3, further comprising: a fixing unit configured to heat and fix animage formed on a recording material by the image forming unit; and atemperature detector configured to detect a temperature of the fixingunit, wherein, when the first instruction information is set as thecolor mode information, the controller controls the fixing unit as thepreparation operation so that a temperature detected by the temperaturedetector is set to a first temperature, and wherein, when the secondinstruction information or the third instruction information is set asthe color mode information, the controller controls the fixing unit asthe preparation operation so that the temperature detected by thetemperature detector is set to a second temperature higher than thefirst temperature.
 12. An image forming apparatus according to claim 11,wherein, when the start instruction is input, the controller controlsthe fixing unit to set the temperature detected by the temperaturedetector to a third temperature higher than the second temperature. 13.An image forming apparatus according to claim 1, further comprising anotification unit, wherein, when the image forming apparatus is in therestricted operation state and the start instruction is input, thecontroller controls the notification unit to notify that the imageformation in the first mode is incapable of being performed.
 14. Animage forming apparatus according to claim 1, wherein each of theplurality of image forming stations includes a photosensitive member onwhich a toner image is to be formed, and wherein, when an amount of useof the photosensitive member of any one image forming station, exceptfor the predetermined image forming station, among the plurality ofimage forming stations reaches a predetermined amount, the controllersets the restricted operation state.
 15. An image forming apparatusaccording to claim 1, wherein each of the plurality of image formingstations includes a developing device storing toner for formation of atoner image, and wherein, when toner is used up in the developing deviceof any one image forming station, except for the predetermined imageforming station, among the plurality of image forming stations, thecontroller sets the restricted operation state.
 16. An image formingapparatus according to claim 1, wherein each of the plurality of imageforming stations includes a photosensitive member on which a toner imageis formed, and a drive unit configured to drive the photosensitivemember, and wherein, when the drive unit of any one image formingstation, except for the predetermined image forming station, among theplurality of image forming stations is incapable of driving thephotosensitive member, the controller sets the restricted operationstate.